Abstract:
This paper details the process of redesigning the weak-post w-beam guardrail, which had shown unacceptable performance in recent crash tests with 2000-kg pickup trucks, using a combination of laboratory experiments, full-scale crash tests, and finite element simulations. The goal of the research was to develop a modified guardrail system that would satisfy the NCHRP Report 350 requirements for Test Level 3. The research addressed three specific design problems: post-rail connection performance, guardrail rupture, and guardrail mounting height. Finite element simulations were used to explore design modifications and evaluate their effects. For instance, a finite element simulation was performed on an early design modification to predict its performance. When this simulation did not predict the rupture that occurred in a full-scale test, a failure condition was added to the material model, allowing the simulation to accurately reproduce the rupture observed in the test. Subsequently, simulations were used to test solutions for this problem, such as adding w-beam backup plates, which the simulations showed reduced effective plastic strain by 38% at the critical location. Finite element simulations were also used to investigate the problem of vehicles overriding the barrier due to an inadequate rail height. These simulations indicated that increasing the rail height by 50 mm would allow the vehicle to be smoothly redirected, a result later confirmed by a full-scale crash test. Finally, a finite element simulation was used to confirm that the higher rail height would not negatively affect performance for small cars, showing that the system would smoothly redirect an 820-kg small car, which was also confirmed by a full-scale test. Overall, finite element simulations were used to explore and validate key design changes, culminating in a system that met all performance criteria.
